Diagnosis and treatment of conditions affecting the brain are among the most difficult and complex problems that face the medical profession. The brain is a delicate soft tissue structure that controls bodily functions through a complex neural network connected to the rest of the body through the spinal cord. The brain and spinal cord are contained within and protected by significant bony structures, e.g., the skull and the spine. Given the difficulty of accessing the brain through the hard bony protective skull the diagnosis and treatment of brain disorders presents unique challenges not encountered elsewhere in the body.
Diagnosis of brain disorders requires clear, accurate imaging of brain tissue through the skull. In recent years significant advances have been made in imaging technology, including stereotactic X-ray imaging, Computerized Axial Tomography (CAT), Position Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). See, for example, Butler U.S. Pat. No. 6,359,959. These imaging devices and techniques permit the surgeon to examine conditions within the brain in a non-invasive manner without opening the skull. If a target lesion or mass is identified through use of one or more imaging techniques, it may be necessary or desirable to biopsy a lesion within the brain. Stereotactic techniques and apparatus for directing a biopsy needle to the site are described and shown, for example, in Cosman U.S. Pat. Nos. 6,331,180 and 6,416,520.
Once a diagnosis has been reached based upon one or more imaging techniques, a treatment plan must be developed. One available method of treatment involves X-ray therapy such as disclosed in Leber U.S. Pat. No. 5,513,238; Shiu U.S. Pat. No. 5,555,283; Cosman U.S. Pat. Nos. 5,748,703, 5,778,043, 5,947,981, 6,459,769; and Kooy U.S. Pat. Nos. 6,005,919, 6,041,101, and 6,278,766. Alternatively, surgical treatment may be necessary or desired. In order to operate surgically on the brain, access must be obtained through the skull and delicate brain tissue containing blood vessels and nerves that can be adversely affected by slight disturbances. Therefore, great care must be taken in operating on the brain not to disturb delicate blood vessels and nerves so that adverse consequences do not result during or after surgery. Brain surgery can be highly invasive. In some instances, in order to obtain access to target tissue, a substantial portion of the skull is removed and entire sections of the brain are retracted to obtain access. Of course, such techniques are not appropriate for all situations, and not all patients are able to tolerate and recover from such invasive techniques. It is also known to access certain portions of the brain by forming a hole in the skull, but only limited surgical techniques may be performed through such smaller openings. In addition, some techniques have been developed to enter through the nasal passages, opening an access hole through the occipital bone to remove tumors located, for example, in the area of the pituitary.
A significant advance in brain surgery is stereotactic surgery involving a stereotactic frame correlated to stereotactic X-ray images to guide a probe or other surgical instrument through an opening formed in the skull through brain tissue to a target lesion or other body. See, for example, U.S. Pat. Nos. 6,331,180 and 6,416,520. A related advance is frameless image guidance, in which an image of the surgical instrument is superimposed on a pre-operative image to demonstrate the location of the instrument to the surgeon and trajectory of further movement of the probe or instrument. Image guided surgery is described, for example, in Guthrie U.S. Pat. Nos. 5,230,623, 5,971,997, 6,120,465, and 6,409,686; Cosman U.S. Pat. Nos. 5,662,111, 5,848,967, 6,006,126, 6,167,295, 6,259,943, 6,275,725, 6,351,661, 6,405,072, 6,662,036, and 6,675,040; and Faro U.S. Pat. Nos. 5,251,127, 5,305,203, and 5,748,767.
Kassam published U.S. patent application 2008/0109026 proposes alternate methods and devices for performing brain surgery involving inserting a cannula with a dilating obturator into the brain to gently dilate the brain tissue. The cannula and dilating obturator may be inserted under image guidance. The cannula provides access to tissue within the brain and provides a working space for the surgeon to perform surgery on structures of the brain, preferably using an endoscope partially inserted into the cannula to visualize the operative site at the end of the cannula. The image from the endoscope may be projected onto a monitor or screen to assist the surgeon and others to visualize the structures of the brain. The present disclosure provides alternative structures and techniques useful in performing surgery in accordance with the techniques disclosed, described or shown in the foregoing application.
Dubrul U.S. Pat. Nos. 5,183,464 and 5,431,676 disclose and describe expandable dilators or trocars useful for accessing hollow body organs. Structures similar to those described by Dubrul have been marketed and sold for laparoscopic access under the trademark STEP by Innerdyne, Inc., and subsequently by the AutoSuture Division of Tyco Healthcare Group, LP (Norwalk, Conn.). Expandable cannula structures having longitudinal wire also are disclosed and described in Bonutti U.S. Pat. No. 5,320,611.
Urban U.S. Pat. No. 5,860,996 discloses and describes an optical trocar for use in laparoscopic surgical procedures. The optical trocar includes a movable cutting blade extendable from a rounded optical window at the distal tip as penetration through tissue is observed through an endoscope inserted into a sleeve until the tip of the endoscope is adjacent to the window. Optical trocars have been marketed for laparoscopic access under the trademark VISIPORT by the AutoSuture Division of Tyco Healthcare Group, LP (Norwalk, Conn.). Penetrating optical trocars also are shown and described in Kaali U.S. Pat. Nos. 5,334,150, 5,376,076, 5,380,291, 5,551,947, 5,609,562, and 5,702,761; Sauer U.S. Pat. Nos. 5,441,041, 5,467,762, 5,569,160, and 6,685,630; Reik U.S. Pat. Nos. 5,271,380, 5,431,151, 5,685,820, and 6,007,481; and Hassler U.S. Pat. No. 5,445,142.